1. Field of the Invention
The present invention relates to a motorized power tool with an output shaft including a tool receptacle proceeding from a free end of the output shaft for receiving a disc-shaped tool and having an outer thread that forms a first securing element for locking means and centering section adjoining the tool receptacle and extending beyond a radial projection of the tool receptacle.
2. Description of the Prior Art
Motorized power tools such as angle grinders or slitting tools, have an output shaft with a tool receptacle and on which a disc-shaped tool, such as a slitting disc, is secured with a locking element such as a locking nut or a locking screw. In order to be able to mount on the output shaft of such a tool simultaneously more than one disc-shaped tool, the power tool is provided with an elongated output shaft as disclosed, e.g., in U.S. Pat. No. 5,303,754. The output shaft has, proceeding from the shaft free end, first section with a tool receptacle in form of a coaxially extending inner thread, and a centering section projecting beyond the radial projection of the tool receptacle.
For mounting of several disc-shaped tools, a hollow cylindrical shaft extension is provided. The shaft extension is secured to the output shaft with a locking element-forming locking screw engaging in the inner thread of the tool receptacle. The shaft extension is pushed onto the output shaft and has, to this end, a first section the inner diameter of which is adapted to the outer diameter of the first section of the output shaft, and a second section that surrounds an end region of the centering section adjacent to the first section of the output shaft.
The drawback of the power tool of U.S. Pat. No. 5,303,754 consists in that in hand-held power tools which inbetween are used with one disc-shaped tool, the large, projecting beyond the disc plane, section of the output shaft limits the possible application region of a power tool.
German Publication DE 871 198 discloses a motorized power tool, the output shaft of which has a proceeding from the shaft free end, tool receptacle having a securing element-forming outer thread, and a centering section adjoining the tool receptacle and projecting beyond the diameter of the outer thread. A disc-shaped tool is secured on the output shaft with locking means-forming locking nut that is screwed onto the outer thread. In order to mount more than one disc-shaped tool on the output shaft, a hollow cylindrical shaft extension is secured on the output shaft. The shaft extension has, at one end, an inner thread engageable with the outer thread of the output shaft. In the end region of the second end of the shaft extension, there is provided an outwardly projecting flange that secures, on the output shaft, a plurality of parallel, spaced from each other, disc-shaped tools, with spacers provided between the disc-shaped tools.
The drawback of the power tool, which is disclosed in the above-discussed German publication, consists in that the shaft extension is guided over the connection section only along mutually engaging threaded sections. With large distances between the disc-shaped tools or with arrangement of several disc-shaped tools on the output shaft, an axial alignment of the shaft extension with respect to the rotational axis of the output shaft cannot be insured. The misalignment can lead to imbalance and, thus, to an imprecise cut. In addition, during an operation, the locking means can become loose or be almost unreleasably tightened.
Accordingly, an object of the present invention is a motorized power tool with an output shaft that would insure a reliable alignment of a shaft extension with the rotational axis of the output shaft upon mounting of the shaft extension on the output shaft, independent from distances between separate disc-shaped tools and/or the number of disc-shaped tools to be mounted on the output shaft.
Another object of the present invention is an output shaft for a motorized power tool that while having a short length, would insure a reliable alignment of the shaft extension, independent of the number of the disc-shaped tools and distances therebetween.
A further object of the present invention is an output shaft for a motorized hand-held power tool that would provide for an easy modification of the power tool from a single disc tool arrangement to a multiple disc tool arrangement, while insuring formation of a precise cut.